Absorption refrigeration system



1970 E. P. PALMATIER 3,524,716

ABSORPTION REFRIGERATION SYSTEM Filed Oct. 23, 1967 EKG-.2 j A 7 M Pam vINVENTOR BY Rw A mZRN United States Patent U.S. Cl. 417-490 7 ClaimsABSTRACT OF THE DISCLOSURE A pump having a rocker arm, hermeticallysealed from outside the pump housing, for transmitting power to thepistons within a pump housing.

7 BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to absorption refrigeration, and more particularly, toabsorption refrigeration systems of the type which employ a pump forforwarding solution from the absorber to the generator of the system.

Description of the prior art In aqua-ammonia absorption refrigerationcycles of the two-pressure variety, it is necessary to pump theaquaammonia solution from the low pressure region of the absorber to thehigh pressure region of the generator. When such cycles are applied toresidential and small commercial air-conditioning duty, the entiresystem is manufactured as a factory assembly with the solution chargefactory installed and the equipment is expected to have long, unattendedservice life. These conditions require that the solution pump design besimple, reliable, low in cost, and, most important, without any form ofsliding contact mechanical seal which could leak aqua-ammonia solutionor vapor.

My issued Pat. No. 3,271,976 described a type of pump that has beenshown to meet these requirements. The design of pump described herein isan improvement over the pump described in Pat. No. 3,271,976, while atthe same time embodying certain novel features.

The design of a suitable pump for forwarding weak absorbent solutionfrom the absorber to the generator of an absorption refrigeration systemof the type which employs ammonia as a refrigerant and water as anabsorbent, presents a number of special problems. In particular, typicalhead pressure requirements for such a pump substantially exceed thatwhich can be satisfactorily achieved with a centrifugal pump. Vane andgear type pumps for this service would be required to operate at a highspeed and could not be lubricated satisfactorily with water, and an oillubrication system would be unsatisfactory due to emulsification of theoil with absorbent solution. They are also unsatisfactory due tocavitation, vapor binding and exhibit high rates of wear due to lowlubricity of the solution being pumped and due to abrasive particlesthat cannot be entirely eliminated from the system. It is thereforedesirable to employ a reciprocating pump for such application becausethey have a positive displacement, and and can operate satisfactorily toproduce high head pressure at slow speeds where lubrication with watercan be satisfactorily achieved.

In a typical air-cooled, ammonia-water absorption sys tem, the high sideor pump discharge pressure may be on the order of about 300 pounds persquare inch gauge and the low side or pump suction pressure may be onthe order of about 50 pounds per square inch gauge. During operation ofthe system, the internal pressures in the pump crankcase may be eitherabove or below atmospheric pressure. On shutdown of the system, thesystem may typically equalize at a pressure of about 200 pounds persquare inch gauge.

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Since ammonia is toxic, it is necessary that the pump be fully hermeticand leak proof in spite of the wide variations in internal pressures towhich it may be subjected. One approach to providing the required degreeof leak tightness is to employ a so-called canned hermetic motor withinthe pump casing. However, this approach is not suited for relativelysmall size absorption refrigeration systems of the type which might beemployed to cool a residence, or small business establishment, becauseof the cost of such an arrangement.

Absorption refrigeration systems, of the type described, normallyutilize a fan for passing air over the evaporator and condenser. Itwould be desirable to use the electric motor driven fan to operate thesolution pump. However, such an arrangement requires the use of asolution pump having an external seal because the fan motor must beoutside the pump housing. The seal of conventional pumps is highlyvulnerable to leakage and such pumps have proved unsatisfactory for theapplication desribed. For example, rubbing type seals always permitssome small amount of leakage to occur which may become excessive intime, particularly in a system employing ammonia, where even a smallamount of leakage is objectionable and where the internal pump pressureis substantially above atmospheric pressure on shutdown. Elastomericseals have previously required bonding to the pump shaft and housing.However, it is virtually impossible to provide a satisfactory sealbetween an elastomeric seal member and a metal shaft or housing by theuse of adhesives alone in an aqua-ammonia system, and clamped seals aredifiicult to retain in position due to the extremes in pressure to whichthey are subjected in this application.

SUMMARY As contrasted with the prior art, described above, the presentinvention provides a novel pump designed to include particularly: (a)the method of sealing and mounting the rocker arm 1 through which themechanical power is transmitted hermetically from outside the pumphousing to the pistons within the housing, (b) the method of mountingthe piston within the pump housing, and (c) the means by which theeffective displacement of the pump may be adjusted to meet therequirements of the system. These and other novel aspects of the designwill be evident from a description of the following drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a vertical section througha single cylinder version of the pump showing the rocker arm seal 3 andone means of mounting the pump cylinder.

FIG. 2 is a horizontal section taken at AA of FIG. 1, showing the methodof mounting rocker arm 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings indetail, the pumping process employed is similar to that of a typicalplunger pump. The particular design shown utilizes a ported cylinder 14and conventional ball check discharge valve 27. The novel features ofthe design are equally well adapted to pumps with hollow ported pistonsand with conventional suction and discharge check valves and no ports incylinder or piston. In the embodiment shown in FIG. 1, the fluid beingpumped enters housing 19 through pipe 18. In an absorption system suchas shown in earlier Pat. No. 3,271,976, housing 19 can serve as acollection chamber for the solution leaving the absorber and a space forthe accumulation and purging of hydrogen and other noncondensibles whichmust be removed from the system periodically.

A body of the fluid 17 is present as a liquid in housing 19. The levelof the liquid surface may be quite variable depending on the rate offlow in through pipe 18, and the quantity delivered by the pump outthrough check valve 27 and discharge pipe 28. On each upward stroke ofpiston 15, its lower end reaches elevation 33 uncovering port 16. Liquidfills the space within the cylinder below piston 15, With flow takingplace from the time the piston uncovers the lower edge of port 16 on theupward stroke until it is closed again on the downward stroke. When port16 has been covered, the volume of liquid below the piston 15, inpassage 39, and the cavity formed by the lower surface of port 22 andcover 26 is trapped and effectively sealed against return to space 17 byrings 40 and 41. Further downward motion of the piston compresses andpressurizes the fluid to above the pressure in line 28. Check valve 27opens and a quantity of fluid is discharged to the high pressure part ofthe system to which the pump is applied.

When piston reaches its most downward position 34, flow through ballcheck 27 stops and spring 42 seats the ball. Upward movement of piston15 results in a low pressure inside cylinder 14 which reaches itsminimum value just as port 16 is uncovered. This contributes to rapidrecharging of the space below the piston, and the cycle is repeated. Itwill be noted that holes are provided in spacer 23 to enable the fluidduring the downward stroke of piston 15 to flow out of cylinder 14,through channel 39, through said holes 25 and ball check 27, todischarge line 28.

Referring now to the novel mechanical details of the disclosure, it willbe understood that one objective of the design is to provide adjustmentof the eflective pump displacement without changing the diameter orstroke of the piston.

A second objective is to minimize the number of bearings that are insidehousing 19. This is particularly important in aqua-ammonia absorptionsystems where the only lubricant available, aqua-ammonia liquid, hasrelatively poor lubricating qualities.

A third objective is to minimize the number of openings required toassemble the internal parts of the pump. A fourth objective is to obtaina maximum piston stroke while at the same time limiting the stress leveldue to bending of rocker arm 1, the size of the opening in nipple 29through which the rocker must enter housing 19, and the diameter andbending stress of the elastomeric seal 3.

The first objective is accomplished in two ways. It is to be understoodthat the number of up and down strokes per minute, and the total travelof push rod 11 are fixed by the revolutions per minute of the shaft, notshown, and the throw of the eccentric or crank, not shown, attached tosaid shaft and driving said push rod. Within limits, turning push rod 11out of clevis 12 and relocking jam nut 10 raises the center position ofbearing center 31 and the extremes of piston stroke 33 and 34. Since thelower edge of port 16 is unchanged, the effective displacement perstroke, the ported pump design is reduced. Second, with the push rodadjustment fixed, the addition of shims 21 and removal of acorresponding thickness of shims 24, will lower the cylinder 14. Thisreduces the distance between the lower edge of port 16 and extremepiston position 34 and reduces the effective displacement. Conversely,adding shims 24, and removing shims 21, increases displacement.

The second objective is achieved by the method of mounting rocker 1 onbearings 5, which are housed in a yoke-like structure 2, which projectstoward the opposite end of the rocker from its point of attachment tothe rocker while remaining outside of seal member 3. This provides afulcrum about which rocker 1 oscillates, using bearings that can be oilor grease lubricated rather than an internal bearing lubricated by thefluid pumped.

The third objective is achieved by inserting the piston and cylinderinto the housing 19 from below along centerline 32, and placing clevis20 over journal pin 31 after rocker 1 has been entered through nipple29, and sealed with elastomeric closure 3 by means of clamps 8. Thiseliminates the need of sliding seals of any'kind'and requires only onebolted cover 26 to close the housing 19.

The fourth objective is achieved by locating fulcrum 30 between the endsof tubular elastomeric seal 3 and providing a generally conicallycontoured rocker 1. The maximum bending moment in rocker 1 occurs whereit is attached to yoke 2 in plane 43-43. The moment reduces toward theend of the rocker engaging clevis 20 so that the diameter of the sectioncan be reduced without exceeding allowable design stress. By observingthe doted representation of the topmost element 35 of the rocker, as itis rotated clockwise to centerline position 37, it is evident that theportion to the right of fulcrum 30 moves down while that to the leftmoves up. The result is that the element becomes generally parallel toan element of tubular nipple 29. At the same time, the bending stress oftubular seal 3 is minimized and easily fabricated parts, such as rocker1, nipple 29, and seal 3 result. It is to be understood that rocker 1could be an integral part of structure 2 rather than being joined andsecured by spring pin 13. Likewise, clamps 8 are only one means ofjoining seal 3 to rocker 1 and nipple 29. Crimped ferrules, flanges nutsand other means, known to the art of joining hose to terminal fittings,may be used with equal or better effectiveness.

A novel feature of the design disclosed is the method of mounting andpositioning the cylinder. It will be recognized that the centerline ofpin 31 follows an arc of a circle around fulcrum 30. Thus, thecenterline 32 of piston 15 and cylinder 14 must rotate a small amounteither side of some average position around a point locatedapproximately at 44. By design, when the piston is in mid-positionshown, centerline 32 is slightly to the left of mean position whereaswhen extreme positions 33 and 34 are reached, centerline 32 is slightlyto the right. Such an oscillating cylinder is not novel, but it doespermit the rigid attachment of piston 15 to clevis 20. It also wouldpermit the use of an integral part instead of two parts 15 and 20secured by spring pin 45. Such an integral part could, for example, bemade from molded carbon graphite, which would provide good bearingproperties for contact with cylinder 14 and pin 31.

It will be noted that the upper surface of 22 is generally sphericalproviding relief from the flat surface of the mating flange 46 oncylinder 14. Also, during the upward stroke of piston 15, a lowerpressure will exist in the cavity below 22, than that above 22, thelatter being in essential communication with space 17. Part 22 will beforced down by a small amount of clearance, which is left in the stackof shims 24, spacer 23, part 22, the thickness of flange 46 and shims21. This will release cylinder 14 and allow it to rock. On the downwardpressure stroke, part 22 will be forced upward by the pressuredifference across 0 ring seal 40, and clyinder flange 46 will be firmlyclamped against shims 21. However, the clamping will be of the type ofan hydraulic spring so that the resistance to rocking of cylinder 14 islimited. It is evident that this provides positive positioning of thecylinder while still allowing the required oscillation, and is superiorto a mechanical attachment of any kind.

While the description given refers primarily to a liquid pumping means,many of the novel details are applicable to similar devices, such as gasand vapor compressors. It is not intended therefore that any limitationis implied by the means described.

I claim:

1. In a hermetic system an hermetic pump or compressor comprising ahermetically sealed housing, said rocker arm extending through saidhousing from outside a hermetically sealed housing containing the fluidto be pumped into said housing containing said fluid, a fluid tightflexible tube, having one end attached to said rocker arm, and the otherend attached to said housing, and wherein said flexible tube serves as aclosure for the hermetic systern allowing mechanical motion to betransferred from outside the hermetic system to a piston inside thehermetic system, said rocker arm being fulcrumed outside of saidfluid-tight tube.

2. An hermetic pump or compressor, as described in claim 1, wherein theaxis around which said rocker arm oscillates, is establishedlby ayoke-like extension to-said rocker arm which contains bearings locatedon a centerline essentially at rightgangles to said rocker arm, andlocated generally between the area of attachment of said flexible memberto said' rocker arm and the area of attachment of said flexible memberto said housing.

3. An hermetic pump or compressor, as described in claim 1, wherein themechanical power required to pump the fluid in said hermetic system isapplied to the end of the rocker arm outside the hermetic system at apoint beyond the area of attachment of said flexible member, and whereinthe pump pistons, piston rods, or other mechanical parts used to impelthe fluid in the hermetic system are attached to thejopposite end ofsaid rocker arm.

4. An hermetic pump, as described in claim 1, in which the mechanicalpower is transferred to a piston within the hermetic systein by means ofan orbital motion of said rocker arm about a center located generallybetween the areas of attachment of said flexible member to said rockerarm and said housing, and wherein said center is established by abearing, housed within yoke-like, or cup-like, extensions of said rockerarm attached to the portion of said rocker arm projecting outside ofsaid hermetic system.

5. An hermetic pump, as described in claim 1, wherein the cylinder issecured at one end by clamping of a flange-like extension and whereinthe clamping force is provided by the hydraulic pressure produced by thepump piston acting on one of the clamping parts which itself acts as apiston.

6. An hermetic pump, as described in claim 1, in which the cylinder issecured at one end by clamping of a flange-like extension of saidcylinder between a fixed part and an axially moveable part which actslike a hydraulic piston to position and force said flange-like extensionof the cylinder against the fixed part.

7. An hermetiepump, as described in claim 1, in which two stacks ofshims, in cooperation with a flange-like extension of the cylinder andparts between which said flange-like extension is clamped, serve tolocate the ports in the cylinder in; relation to the extremes of thepiston travel so as to effectively establish the displacement of thefluid during each stroke of the piston.

References Cited UNITED STATES PATENTS 1,736,973 11/1929 King 7418.1 XR3,247,731 4/1966 Chapman 7418.1 3,281,065 10/1966 Chafliotte 7418.1 XR

ROBERT M. WALKER, Primary Examiner U.S. Cl. X.R.

